Reduced inspiratory muscle strength leads to limited vital capacity, shortening and weakness of chest wall with associated poor ventilation, ineffective cough, and decreased exercise tolerance. We observed that a four-week IMT with PR program improves respiratory muscle strength and exercise capacity in NSCLC patients during RT. This is of great importance because patient symptoms usually worsen as time goes by.
To our knowledge, this study is the first to report the effectiveness of IMT with PR on muscles and exercise capacity in patients with NSCLC receiving RT. Our study used various physical assessment methods to help understand NSCLC patients during RT.
Many physical symptoms, such as dyspnea, fatigue, and pain, can appear during RT. RP or pulmonary inflammation due to RT can cause significant morbidity and occasionally mortality following thoracic RT [21]. Clinical RP was experienced by 20% of NSCLC patients. The risk factors included poor performance status, low pulmonary function, comorbid lung disease, smoking history, and surgical resection [4]. Therefore, improving performance status and exercise capacity is important even during radiation treatment periods.
In our study, MIP significantly improved after IMT with PR. MEP and PCF did not significantly improve but improved at post-evaluation. In previous randomized clinical trials (RCTs), inspiratory muscles and aerobic exercise training significantly facilitated respiratory muscle strength recovery, increased lung volume, and improved the distance covered in the 6MWT in NSCLC patients after video-assisted thoracoscopic surgery. These improvements were observed as early as the second week and were sustained up to 12 weeks. This study included the early stage of NSCLC after video-assisted thoracoscopic surgery. In this study, MIP (60.1 ± 25.1 vs 72.5 ± 31.9 cmH2O, p = 0.005) lowered compared to MIP (71.6 ± 34.9 vs. 94.3 ± 32.8 cmH2O, P = 0.018) in previous RCTs [22]. Another study reported that additional IMT in patients at high risk of PPC significantly improved oxygenation up to 5 days after the surgery when compared with standard physiotherapy alone. However, no differences in respiratory muscle strength or walked distance were detected between groups [23].
In our study, there was no difference between FVC, FEV1, and baseline after 4weeeks. Improvements in physiological index of lung capacity may be difficult to attain in NSCLC. In addition, there was no improvement in dyspnea symptom in EORTC C30 and LC13. This was different from the result reported in another RCT that IMT training is effective against dyspnea and breathlessness in patients with thoracic malignancies. This may be the effect during RT, which may cause various physical symptoms. Symptoms such as appetite loss, dysphagia, and chest pain did not change significantly after 4 weeks but tended to increase. In addition, the duration and intensity of training was different. In this study, the protocol comprised five IMT sessions weekly for 12 weeks for a total of 30 min/day. The initial training was set as 40% and progressed to a maximum of 70% PImax compared our protocol which progressed from 30% PImax to 50% PImax.
Our program was ineffective as regards the breathlessness symptom; however, it was effective in improving inspiratory muscle and exercise tolerance. The 6MWT, CET, and strength of lower extremities significantly improved after IMT with PR. There are some studies regarding rehabilitation in patients with NSCLC receiving RT. Simultaneous PR improved pulmonary function, particularly in measures of FEV1, and exercise capacity in patients with lung or esophageal cancer even after radiotherapy treatment [24]. Another preliminary study demonstrated that PR programs improved exercise tolerance as measured by the 6MWT among inpatients receiving concurrent chemoradiotherapy [25].
There were several limitations to this study. This study was a retrospective pilot study with a small sample size. PR during RT is not enough evidence. Therefore, PR is not commonly prescribed. There was also no control group. Therefore, the value of these results in clinical practice may be limited. Based on this preliminary pilot results, prospective RCTs can be performed for more supportive evidence that have not been studied yet.